A variety of conventional devices for transporting and storing powder and liquid medium, including those comprising an outer container and inner container having a volume of several hundred liters, are used more and more often in various application. In many of such conventional devices, the inner container comprises plastic materials, wherein the wall can comprise one or several layers. In addition, the inner container has an opening for filling and discharging through its so-called top section and is secured in many cases by means of a covering element in the outer container. The inner container is often realized with a relatively thin wall and is enclosed within an outer container for the purpose of its stabilization. The outer container may comprise metal or plastic materials. In most cases, the outer container is arranged on a pallet that comprises wood, metal or plastic materials.
Applicants have recognized that a metallic outer container is undesired in many fields, in particular in the fields of chemical industry and food processing. For example, in fields in which acids and/or corrosive materials are used, the danger of corroding exists if the outer container is made of steel. Such danger of corroding may be avoided if the outer container is made of stainless steel. However, such a container comprising stainless steel is expensive and lavish with respect to its making.
To eliminate the aforementioned disadvantages, the outer container of certain conventional devices have been produced from plastic materials, wherein the wall of said container can be made of one or of several layers as well. Such an outer container made of plastic materials tends to be inexpensive in its production and not subject to corrosion.
However, Applicants have further recognized that there are fields in industry in which conventional storage devices that have an inner container and/or outer container being made of plastic materials cannot be used for reasons of security with respect to explosions. By using plastic materials, the danger exists that electrostatic charging may occur due to poor electrical conductance. This may also lead to electrostatic surface charge effects.